Roll for papermaking machinery

ABSTRACT

THIS INVENTION IS DIRECTED TOWARD MEANS FOR REMOVING THE MOIST AIR WHICH TENDS TO COLLECT IN TENT-LIKE POCKETS IN THE DRYER SECTION OF A PAPERMAKING MACHINE. SUCH REMOVAL IS ACCOMPLISHED BY PROVIDING GUIDE ROLLS WHICH HAVE A PLURALITY OF GROOVES THEREIN TO SUPPLY FRESH AIR INTO THESE POCKETS AND FORCE THE MOIST AIR OUT. THE CONSTRUCTION OF THE GROOVES IS SUCH AS TO REDUCE SUBSTANTIALLY, IF NOT ELIMINATE ENTIRELY, THE TENDENCY OF A DYER FABRIC TO CREEP OR &#34;WALK&#34; OFF THE MACHINE ROLLS.

United States Patent 3,555,700 ROLL FOR PAPERMAKING MACHINERY JosephRobert Wagner, Norristown, Pa., assignor to Huyck Corporation, Stamford,Conn., a corporation of New York Filed Aug. 15, 1967, Ser. No. 660,623Int. Cl. F26b 13/00 U.S. Cl. 34-116 3 Clams ABSTRACT OF THE DISCLOSUREThis invention is directed toward means for removing the moist air whichtends to collect in tent-like pockets in the dryer section of apapermaking machine. Such removal is accomplished by providing guiderolls which have a plurality of grooves therein to supply fresh air intothese pockets and force the moist air out. The construction of thegrooves is such as to reduce substantially, if not eliminate entirely,the tendency of a dryer fabric to creep or "walk of the machine rolls.

BACKGROUND OF THE INVENTION In the typical papermaking machine such asthe socalled fourdrinier machine, an aqueous suspension of fibers,called the furnsh, is flowed onto a travelling forming medium, generallyan endless belt of WoVen metal Wire and/ or synthetic material, to forma continuous Web of paper or paper-like material (such as board, pulp,asbestos sheet and the like). As the furnish" travels through theforming section of the machine, much of its Water content is removed andthe continuous Web is made self-supporting to some extent. This waterremoval is enhanced 'by the use of' well-known devices such ashydrofoils, table rolls and/or suction boxes.

After leaving the forming section of the machine, the somewhatself-supporting Web is transferred to the press section of the machineWhere still more of its water content is removed by passing it through aseries of nips formed 'by cooperating press rolls. It should be notedthat these press rolls also serve to compact the Web as well as removewater therefrom.

The paper Web is then transferred to the dryer section of the machinewhere it is passed about one or more arrays of heated, generallycylindrical rolls to remove still further amounts of Water therefrom. Inmost instances, these dryer rolls are arranged in upper and lowerparallel arrays With the continuous web being passed to and fro betweenthe arrays in a serpentined manner about each of the rolls. Generally,the surface of the dryer rolls Will be smooth and imperforate With theconr tinuous Web being held in intimate heat transfer relation therewithover at least a portion of the surface thereof by an endless backingfabric or belt (commonly referred to as a dryer felt or dryer fabric).However, recent technical advances in the papermaking art have shownthat in some instances it may be desirable to construct the dryer rollsurface so as to be pervious and blow steam or other suitable dryingmedia therethrough in order to increase the amount of water removed fromthe Web.

In the past, dryer fabrics have generally been made of a relativelyimpervous, blanket-like construction. However, a modern trend is to usea fluid permeable construction, generally of natural or syntheticfibers. Open weave fabrics generally have been found desirable for suchpurposes as they are readly permeable to such fluids; however, in someinstances, non-woven Structures such as perforated plastic belts or thelike have also been found suitable.

In the dryer section of the machine, there is a tendency 3,555,700Patented Jan. 19, 1971 ice for the steam and/or moisture laden air whichis liberated from the paper Web to become trapped in pockets within themachine. Some of these pockets are formed 'by the dryer fabrics aloneand comprise the areas enclosed 'by the dryer fabrics as they traveltheir endless paths. Other of these pockets are located between theupper and lower arrays of dryer rolls; these pockets being tent-likeareas enclosed by a dryer roll surface, the paper Web and the oppositedryer fabric. As the build-up of moisture in these pockets hinders theremoval of water from the paper Web and as this build-up may tend tocreate a non-uniform moisture profile in the Web, it is desirable toprovide means for exhausting the moist air from, or otherwise preventingit from building-up in, these pockets.

In many instances, large blowers or eXhaust fans have been used to movefresh air laterally through the dryer pockets in an attempt to exhaustthis moist air and introduce fresh air therein. However, thesearrangements generally require a fairly large capital expenditure andWhere large machine operating widths are encountered, such anarrangement may also create rather than prevent the creation 0f anon-uniform moisture profile in the paper Web; Still further, should theair-flow into these pockets be under too great a pressure; sheet fluttermay occur causing Wrinkling or possibly breaking of the paper Web.

Other methods of introducing fresh air into the dryer pockets includemechanically 'blowing air through or around those fabric guide rollsdisposed between adjacent dryer rolls and through the dryer fabric intothe pockets. However, these methods entail the use of suitable andhighly reliable sealing means in order to prevent escape of airtherearound and also have practical limits as to the amount of pressurethat may be used to force the air into the pockets.

Therefore, one object of the present invention is to provide animproved, simplified means for preventing the build-up of moist air inthe pockets of the dryer section of a papermaking machine.

Another object of the present invention is to provide improved means forexhausting moist air from the dryer pockets in a papermaking machineWithout disturbing the paper Web and without creating a tendency for thedryer fabric to creep or walk toward one edge of the machine.

Another object of the present invention is to provide a simplified meansfor maintaining a uniform moisture profile in a continuous paper sheetWithout creating a tendency for the dryer fabric to walk off themachine.

SUMMARY OF THE INVENTION In accordance With the principles of thisinvention, in one embodiment thereof, there is included in a papermakingmachine having at least one array of heated, generally cylindrical rollsfor drying a continuous Web of paper which is passed about and held inheat transfer relation therewith by means of associated fluid permeablebacking fabric (dryer fabric); a plurality of guide rolls over Which thebacking fabric passes and Which maintain the backing fabric on themachine. Some of these guide rolls will be disposed between adjacentdryer rolls with these guide rolls being referred to as "pocket rolls.At least one pocket roll is constructed to have at least one groove of apredetermined pattern in the surface thereof, Which groove or grooveswill contact the dryer fabric and extend from a point approximatelymid-Way between the ends of the roll toward the opposite ends of theroll in mirror image segments. This arrangement causes air to beintroduced into the tent-like pockets of the machine and alsosubstantially reduces, if not eliminates entirely, the tendency of thebacking fabric to walk-off the machine. Preferably, the predeterminedpattern will be a continuous helix with each roll having a plurality ofsuch grooves.

Additional objects and advantages of this invention together with abetter understanding thereof may be had by referring to the followingdetailed description thereof together With the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cabinet view of the dryersection of a papermaking machine in which this invention may beincorporated;

FIG. 2 is a cabinet view of a pocket roll constructed in accordance withthe principles of this invention; and FIG. 3 is a cabinet view of analternate construction of the pocket roll of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, thereis shown the dryer section of a papermaking machine comprising a firstor upper array of dryer rolls including cylinders 10, 12 and 14 with asecond or lower array of dryer rolls including cylinders 16, 18 and 20being vertically spaced therefrom. The dryer rolls are preferablysmooth, imperforate metal cylinders arranged for rotation upon suitablebearings (not shown) and supplied with steam which is introduced intothe interior portions thereof at suitable temperatures. As previouslymentioned, in some instances, the surface of one or more of the dryerrolls may be made gas pervious and heated air or steam blowntherethrough to increasc drying of the paper web. Preferably, the upperand lower arrays of the dryer rolls will be arranged in staggered rows,as shown in FIG. l, With the rolls in one array being oifset withrespect to the corresponding roll in the other array.

A continuous Web 22 of paper or other similar sheetlike material isshown as travelling from left to right in the drawing. The paper Web 22is received from the press section (not shown) of the machine and isguided upwardly and over the dryer roll 10, downwardly and around lowerdryer roll 16, back up and around upper roll 12 and so forth untilultimately it is passed around each of the dryer rolls in a generallyserpentined manner. When the paper Web 22 leaves the dryer section ofthe machine, it is generally passed through a calendar stack (not shown)to provide it With a smooth finish and then collected on a suitable reel(not shown).

Means are provided for guiding the paper Web 22 through the dryersection and maintaining it in intimate heat transfer relation With eachof the dryer rolls. Accordingly, a first fluid permeable backing fabric26 is associated with the upper array of dryer rolls (-14) and isarranged to contact the paper web 22 and maintain it in intimate heattransfer relation with the rolls in the upper array, in this instance byholding it against the rolls 10, 12 and 14. Similarly, a second fluidpermeable backing fabric 28 is associated with the lower array of dryerrolls and is also arranged to contact the paper Web 22 and maintain itin intimate heat transfer relation with the dryer rolls in the lowerarray, again in this instance holding it against the rolls 16, 18 and20. Preferably, both dryer fabrics 26 and 28 will be identical inconstruction and can be made endless either by seaming or being woven assuch.

According to the principles of this invention, each of the dryer fabrics26 and 28 will be of a fluid permeable construction. Open weave fabricsand the like have generally been found desirable as they readily permitthe passage of fiuids therethrough; however, in some instances,non-woven Structures such as perforated plastic belts and the like havealso been found desirable. However, it is not the intention of thisinvention to be limited to a specific dryer fabric construction as theyare set forth by way of example only. This invention only requires thatthe dryer fabrics readily permit the passage of fluids, such as air,water vapor and the like, therethrough.

Each dryer fabric travels about a predetermined closed or endless pathwhich in this instance is defined by its associated array of dryer rollsand a plurality of fabric guide rolls which extend across the width ofthe fabric and which maintain sufficient tension thereon to ensureproper operation thereof. In the example shown in FIG. 1, the upperfabric 26 has associated therewith a plurality of guide rolls 30-36which are disposed in a desired predetermined manner. In thisarrangement, certan of the guide rolls 31, 32 Will be disposed betweenadjacent dryer rolls (these guide rolls hereinafter being referred to aspocket rolls' As seen in FIG. 1, pocket roll 31 is disposed betweendryer rolls 10 and 12 and preferably is positioned to have its centerline disposed below the center line of the associated dryer rollswhereas pocket roll 32 is disposed between dryer rolls 12 and 14 andalso is positioned to have its center line below the center line of theassociated dryer rolls.

In like manner, the lower dryer fabric 28 has associated therewith aplurality of guide rolls 40 46 which are also disposed is apredetermined manner and which combine with the lower array of dryerrolls to define the path of travel of the lower dryer fabric 28. Certainof the lower guide rolls 41, 42 are disposed between adjacent associateddryer rolls, these guide rolls also hereinafter being referred to aspocket rolls. Accordingly, pocket roll 41 is disposed between lowerdryer rolls 16 and 18 and preferably is positioned to have its centerline disposed above the center line of the associated dryer rollswhereas pocket roll 42 is disposed between dryer rolls 18 and 20 andalso has its center line disposed above the center line of theassociated guide rolls.

As can be seen in FIG. 1, tent-like pockets lie between the upper andlower arrays of dryer rolls. For purposes of convenience, and in orderto facilitate discussion of this invention, these tent-like pockets arenumbered 50, 52, 54 and 56 respectively. It should be noted that it isin these areas of the machine that there is a tendency for the moist airevaporated from the paper web to collect. As mentioned previously, ifthis moist air is not removed or otherwise prevented from building up,further removal of water from the paper Web will be inhibited. Further,as greater amounts of moist air tend to accumulate in the centralportions of the machine (as one looks across the width thereof), thereis a danger that the rate of water removal from the paper Web Will varyacross the width of the sheet and thus create a non-uniform moistureprofile in the paper Web 22.

In accordance with the principles of this invention, and referring nowto FIGS. 2 and 3, means are provided for introducing air into thesetent-like pockets to drive out or purge the moist air therefrom, but insuch a way as not to create any danger of tearing the paper Web orcreating any force on the dryer fabric which will cause it to creep orwalk toward one edge of the machine. Specifically, this inventioncontemplates constructing at least one pocket roll to have at least asingle groove, and preferably a plurality thereof, therein WhichContacts the fabric. These grooves are constructed in such a manner asto eX- tend substantially across the entire width of the roll and from apoint approximately mid-way between the opposite ends thereof, eachgroove extends toward the opposite ends of the roll in predeterminedmirror-image segments. Such a roll will substantially reduce thetendency of the fabric to creep or walk off the machine rolls becauseany force created on the fabric as it passes over the grooves will haveequal and opposite directing components, due to the mirror-image'grooves eifectively dividing the roll into two halves. When the fabricis centrally located on the machine, these forces will tend to Cancelone another so that there is no net force created which can causecreeping or walking of the fabric toward one or the other of the lateraledges of the machine. However, even where the fabric has already startedto "walk off the machine, such a roll as has hereinbefore been describedwill tend to force the fabric back onto the machine. This is due to thegrooves in the roll creating a net force on the fabric which is in adirection opposite to that in Which the fabric is travelling. Thislatter effect is due to the fabric being in contact with a greatersurface on one side of the roll than the other and thus the rotation ofthe roll together with the grooved surface thereof tends to cause thefabric to position itself correctly on the machine.

While not wanting to be bound by a theory of operation, it is believedthat the improved air movement in the dryer pocket is the result of thecentrifugal forces acting on the air within the grooves of the pocketroll. In other words, air entrained in the grooves of the pocket rollWill be forced to the outer portions thereof and through the dryerfabric as the pocket roll rotates thus causing the air to be forced intothe tent-like pockets.

In the preferred embodiment of the invention, and referring now to FIG.2, the pocket roll will be constructed by attaching a plurality ofmirror-image, helically-shaped vanes 60 to a suitable hub or support 62.The vanes 60 can be Secured to the hub 62 in any number of satisfactorymethods as by dovetailing them in suitable slots on the hub, bondingthem thereto with a suitable adhesive, welding, brazing or any othersuitable method of attachment. Preferably, the hub 62 will be agenerally cylindrical body Which is mounted to the machine structure(not shown) for rotation about its longitudinal axis. The hub, vanes orboth may be constructed of aluminum, sheetmetal, a suitable plastic orany other suitable material and preferably the vanes and the hub Willboth be constructed of the same material.

An alternate construction for the specially designed pocket rolls ofthis invention and referring specifically to FIG. 3 is to provide agenerally cylindrical body 68 having predetermined mirror-image grooves70 cut therein, as by machining. Again, the groove or grooves WilleXtend from the center of the roll toward the opposite ends thereof inmirror-image segments, preferably helical. The material from Which theroll is constructed may be any suitable material Which is generallyresistant to the compression forces of the fabric as it passes over thesurface thereof in order that the grooves in the roll remainsubstantially incompressible as the fabric passes thereover.

As can be seen from the above discussion, fresh air will be supplied tothe dryer pockets of a papermaking machine While actively deterring anytendency of the dryer fabric to creep laterally or Walk off the machine.Still further, such an arrangement requires only minor modification toexisting papermaking machinery and does not entail extensive orelaborate designing of new machinery.

Thus, having described only a particular embodiment of the presentinvention, it Wil 1 become obvious to those skilled in the art thatvarious changes and modifications may be made thereto Without departingfrom its scope in its broader aspect. As such, it is the intention ofthe appended claims to cover all such changes and modifications Whichfall within the true spirit and scope of the present invention.

What I claim as new and novel and desire to secure by Letters Patent ofthe United States is:

1. Apparatus for removing moisture from a continuous Web of sheetmaterial comprising:

At least one array of heated, generally cylindrical rolls for removingmoisture from a continuous Web of sheet material which is passed aboutand held in heat transfer relation therewith,

an endless, fluid permeable belt for guiding said continuous Web ofsheet material about said array of dryer rolls and for maintaining saidcontinuous web in heat transfer relation With said array of rolls, and

A plurality of fabric guide rolls for maintaining said endless belt inguiding relation with said continuous Web of sheet material, at leastone of said fabric -guide rolls being disposed between adjacent dryerrolls and having at least one groove of a helical pattern thereinextending from a point approximately mid-way between the opposite endsof said roll toward the opposite ends thereof in substantiallymirror-image segments of one another, said helical groove eXtending inthe direction in which said roll rotates when in use.

2. Apparatus as described in claim 1 wherein said grooved fabric guideroll comprises a generally cylindrical member having at least one groovein the peripheral surface thereof.

3. Apparatus as described in claim 1 wherein said grooved fabric guideroll comprises a generally cylindrical member having a plurality ofspaced vanes attached to the peripheral surface thereof to form aplurality of grooves therebetween.

References Cited UNITED STATES PATENTS 664,861 1/1901 Hentschel 29 1213,339,818 9/1967 Morrow 29-121X 3,405,884 10/1968 Patterson, Jr 29-121X3,445,938 5/1969 Clark 34-116 REUBEN F RIEDMAN, Primary Examiner T, A.GRANGER, Assistant Examinr

